Abstract: Box beam is a common beam structure in undergraduate mechanics teaching. A warping shape function suitable for box beam section was proposed. Based on the new warping shape function, a high-order shear deformation beam theory suitable for box beams was developed. The proposed theory considers the influence of shear deformation and moment of inertia simultaneously, and no shear correction factor needs to be introduced. Therefore, it owns high accuracy for dynamic and static mechanical behavior. Furthermore, the proposed theory possesses a simple calculation procedure and is easy to be applied in engineering, which can be used as a teaching example of mechanics of materials, elasticity mechanics and finite element method, and can also be utilized to develop a novel one-dimensional high-precision finite element beam model.